Collect red top or green top Heparin, send 2.0 mL serum/plasma. Centrifuge, separate serum/plasma within two hours of collection, transfer to a plastic transport tube, indicate sample type on tube and send.
The use of gel-barrier tubes is not recommended.
Liquid chromatography/tandem mass spectrometry (LC/MS-MS)
Room temp: 3 days, Refrigerated: 7 days, Frozen: 7 days
Therapeutic drug management.
Trough levels are most reproducible.